raid: make RAID autodetect default a KConfig option

RAID autodetect has the side effect of requiring synchronisation
of all device drivers, which can make the boot several seconds longer
(I've measured 7 on one of my laptops).... even for systems that don't
have RAID setup for the root filesystem (the only FS where this matters).

This patch makes the default for autodetect a config option; either way
the user can always override via the kernel command line.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: NeilBrown <neilb@suse.de>

2 files changed, 23 insertions, 2 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 07d92c11b5d8..8e72c916535f 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -30,6 +30,20 @@ config BLK_DEV_MD
 
           If unsure, say N.
 
+config MD_AUTODETECT
+        bool "Autodetect RAID arrays during kernel boot"
+        depends on BLK_DEV_MD
+        default y
+        ---help---
+          If you say Y here, then the kernel will try to autodetect raid
+          arrays as part of its boot process. 
+
+          If you don't use raid and say Y, this autodetection can cause 
+          a several-second delay in the boot time due to various
+          synchronisation steps that are part of this step.
+
+          If unsure, say Y.
+
 config MD_LINEAR
         tristate "Linear (append) mode"
         depends on BLK_DEV_MD
diff --git a/init/do_mounts_md.c b/init/do_mounts_md.c
index c0dfd3c1e91b..48b3fadd83ed 100644
--- a/init/do_mounts_md.c
+++ b/init/do_mounts_md.c
@@ -12,7 +12,12 @@
  * The code for that is here.
  */
 
-static int __initdata raid_noautodetect, raid_autopart;
+#ifdef CONFIG_MD_AUTODETECT
+static int __initdata raid_noautodetect;
+#else
+static int __initdata raid_noautodetect=1;
+#endif
+static int __initdata raid_autopart;
 
 static struct {
         int minor;
@@ -252,6 +257,8 @@ static int __init raid_setup(char *str)
 
                 if (!strncmp(str, "noautodetect", wlen))
                         raid_noautodetect = 1;
+                if (!strncmp(str, "autodetect", wlen))
+                        raid_noautodetect = 0;
                 if (strncmp(str, "partitionable", wlen)==0)
                         raid_autopart = 1;
                 if (strncmp(str, "part", wlen)==0)
@@ -288,7 +295,7 @@ void __init md_run_setup(void)
         create_dev("/dev/md0", MKDEV(MD_MAJOR, 0));
 
         if (raid_noautodetect)
-                printk(KERN_INFO "md: Skipping autodetection of RAID arrays. (raid=noautodetect)\n");
+                printk(KERN_INFO "md: Skipping autodetection of RAID arrays. (raid=autodetect will force)\n");
         else
                 autodetect_raid();
         md_setup_drive();